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[Sudoku123456789]

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Please explane solution


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[Sudoku123456789]

Tried many techniques. Explain solution please.

[Sudoku123456789]

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[JC Van Hay]

In spite of the lack of marking of the bilocals in the possibibity matrix, the bivalues fortunately lead to a simple solution. To wit, the 2 solutions of R1 exclude 5r5c4; stte

Code: Select all

+--------------------+----------------------+-----------------+
| 3     7     (89)   | 4       5      1     | 2     6(9)  68  |
| 4     28    2589   | 7       389    6     | 589   1     38  |
| 5689  68    1      | 9(23)   389    28    | 4     35    7   |
+--------------------+----------------------+-----------------+
| 58    238   2358   | 1       7      (258) | 6     4     9   |
| 7     46    456    | -5(36)  34(6)  9     | 18    2     18  |
| 1     9     246(8) | (26)    4(68)  24(8) | 3     7     5   |
+--------------------+----------------------+-----------------+
| 689   1468  4689   | 569     2      457   | 1579  35    136 |
| 2     5     7      | 8       19(6)  3     | 19    (69)  4   |
| 69    1346  3469   | 569     1469   457   | 1579  8     2   |
+--------------------+----------------------+-----------------+


8r1c3 -> 8r6c56; 5r4c6 or 2r4c6, 2r3c4, 3r5c4 => -5r5c4
or
9r1c3 -> 9r8c8, 6r8c5, hidden triple (236)r356c4 => -5r5c4

Other ways to proof -5r5c4 :

1. Forbidding matrix :

Code: Select all

 5r5c4
|3r5c4 3r3c4      |
|      2r3c4 2r6c4|
|6r5c4       6r6c4|6r56c5
                   6r8c5  6r8c8
                          9r8c8 9r1c8
                                9r1c3 8r1c3
                                      8r6c3 8r6c56
 5r4c6       2r4c6                          8r4c6  : IOW 5r5c4 -> r4c6 is empty


2. This wysiwyg forbidding matrix can be written in Eureka notation as a Kraken Cell (258)r4c6 :
HT(236)r356c4=6r56c5-6r8c5=(6-9)r8c8=9r1c8-(9=8)r1c3-8r6c3=8r6c56-8r4c6=*Wing[(5=*2)r4c6-2r6c4=(2-3)r3c4=3r5c4] -> derived SIS/constraint {3r5c4, 6r5c4, 5r4c6} :=> -{5r5c4}; stte

3. ...

[Sudoku123456789]

Sorry, i'm very new to this.

Are there any guides available to this terminology?

Thanks in advance for the solution.

[JC Van Hay]

http://sudoku.com.au/sudokutips.aspx?Go=B12-4-1999
http://sudopedia.enjoysudoku.com/
http://forum.enjoysudoku.com/collection-of-solving-techniques-t3315.html

[Sudoku123456789]

Thank you JC for the many help. I unfortunately have 1 last question.

Which technique did you use to validate -5r5c4? Is this the chaining technique?

[JC Van Hay]

http://www.sudokuwiki.org/Cell_Forcing_Chains applied twice : first from (89)r1c3, then from (25)r4c6 for one of the chain.